Regulation of Pseudomonas aeruginosa hemF and hemN by the dual action of the redox response regulators Anr and Dnr

Mol Microbiol. 1998 Aug;29(4):985-97. doi: 10.1046/j.1365-2958.1998.00980.x.


The oxidative decarboxylation of coproporphyrinogen III catalysed by an oxygen-dependent oxidase (HemF) and an oxygen-independent dehydrogenase (HemN) is one of the key regulatory points of haem biosynthesis in Pseudomonas aeruginosa. To investigate the oxygen-dependent regulation of hemF and hemN, the corresponding genes were cloned from the P. aeruginosa chromosome. Recognition sequences for the Fnr-type transcriptional regulator Anr were detected -44.5 bp from the 5' end of the hemF mRNA transcript and at an optimal distance of -41.5 bp with respect to the transcriptional start of hemN. An approximately 10-fold anaerobic induction of hemN gene expression was mediated by the dual action of Anr and a second Fnr-type regulator, Dnr. Regulation by both proteins required the Anr recognition sequence. Surprisingly, aerobic expression of hemN was dependent only on Anr. An anr mutant did not contain detectable amounts of hemN mRNA and accumulated coproporphyrin III both aerobically and anaerobically, indicating the importance of HemN for aerobic and anaerobic haem formation. Mutation of hemN and hemF did not abolish aerobic or anaerobic growth, indicating the existence of an additional HemN-type enzyme, which was termed HemZ. Expression of hemF was induced approximately 20-fold during anaerobic growth and, as was found for hemN, both Anr and Dnr were required for anaerobic induction. Paradoxically, oxygen is necessary for HemF catalysis, suggesting the existence of an additional physiological function for the P. aeruginosa HemF protein.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aerobiosis
  • Amino Acid Sequence
  • Anaerobiosis
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Base Sequence
  • Chromosome Mapping
  • Cloning, Molecular
  • Coproporphyrinogen Oxidase*
  • Coproporphyrinogens / metabolism
  • DNA Primers / genetics
  • DNA, Bacterial / genetics
  • DNA-Binding Proteins*
  • Gene Expression Regulation, Bacterial
  • Genes, Bacterial
  • Molecular Sequence Data
  • Mutation
  • Oxidation-Reduction
  • Pseudomonas aeruginosa / genetics
  • Pseudomonas aeruginosa / growth & development
  • Pseudomonas aeruginosa / metabolism*
  • RNA, Bacterial / genetics
  • RNA, Bacterial / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Trans-Activators*
  • Transcription Factors / metabolism*


  • Bacterial Proteins
  • Coproporphyrinogens
  • DNA Primers
  • DNA, Bacterial
  • DNA-Binding Proteins
  • DNR protein, Pseudomonas aeruginosa
  • RNA, Bacterial
  • RNA, Messenger
  • Trans-Activators
  • Transcription Factors
  • ANR protein, Pseudomonas aeruginosa
  • coproporphyrinogen III
  • HemN protein, Bacteria
  • Coproporphyrinogen Oxidase